Method of making cold worked hollow stem valves



Jan. 23, J. M KERW|N ET AL l METHOD OF MAKING COLJD WORKED HOLLOW STEM VALVES Filed March ll, 1942 2 Sheets-Sheet 1 J. M. Kl-:RwlN ET AL Jan. 23, 1945. 2,367,783

METHOD OF MAKING COLD WORKED HOLLW STEM VALVE-IS Flled March 11, 1942 2 Sheets-Sheet 2 ?atented Jan. 23, 1945 METHOD OF MAKING COLD WORKED HOLLOW STEM VALVES John M. Kerwn and Samuel H. Norton, Cleveland, Ohio, assignors to Thompson Products. Inc., a corporation of Ohio Application March 11, 1942, Serial No. 434,237

(Cl. 2li-156.7)

2 Claims.

More specifically the invention relates to the production of hollow poppet valves having cold worked internally ribbed stems.

Hollow poppet valves are subjected, in operation, to severe tensile stress-es and any circumferentially extendingy scratches in the hollow valve stem are very dangerous because they can readily form loci for fatigue cracks.v Since it is highly desirable to decrease the weight of a hollow valve as much as possible, thin stem walls are used. These stem Walls, nevertheless, must be capable of resisting the heavy tensile loads applied thereon, and it is an important feature .of this invention to increase thestrength of hollow valve stems by cold working. The stems can be internally ribbed during the cold werking oneration. 'Ihe -ribs extend longitudinally of the stem and obliterate or at least break up any circumferential scratches in the stem wz ll.

Cold working the valve stem metal will increase the tensile strength of the metal and the simultaneous internal ribbing of the stem will further increase its tensile strength. The ribs, in addition, serve as cooling ns to dissipate heat from the coolant in the hollow valve through the stem wall.

Thus the dangerous scratches and cracks are removed, a higher rate of heat transfer is obtained, thin stem walls can be used, and the metallurgical properties of the metal are improved.

It is, therefore, an object of this invention to provide a method of making a hollow stemmed poppet valve with an internally ribbed stem.

A further object of this invention is to pro-v vide a method of making hollow stemmed poppet valves having cold worked internally ribbed stems. v

A still further object of this invention is to strengthen hollow poppet valves by cold working.

the same around a mandrel.

Another object of the invention is to improve the metallurgical, characteristics of the metal inV hollow valve stemsA by hammering` the metal aroundma stem. i

AI stillfurther obiect of the invention is to pro.-

vide aYI'nethod ofv mak-ing a lightweight hollow Aiiuted mandrel inserted in the valvev furtherobjects of the invention .will I be apparext-tolthose ,skilled in the art from the `I following detailed description of the annexed sheets of drawings, which, by way of preferred examples, illustrates several embodiments of the invention.

On the drawings:

Figure 1 is asplan View of hammer dies for act-- ing on an inserted valve blank in accordance with this invention.

Figure 2 is a cross-sectional view along the line II-II of Figure 1, illustrating the start of the hammering operation.

Figure 3 is a view similar to Figure 2 illustrat ing the completion of the hammering operation.

Figure 4 is a longitudinal cross-sectional view of a hollow poppet valve blank `made in accordance with this invention.

Figure 5 islan enlarged transverse cross-sectional view along the line V-V of Figure 4.

Figure 6 is a view similar to Figure 5 but illustrating another form of internally ribbed valve stem in accordance with this invention.

Figure '1 is a view similar to Figures 5 and 6, but illustrating a smooth continuous internal surface on the valve stem produced by cold-working the stem around a smooth, polished mandrel in accordance with a still further modified embodiment of the invention. v

Figure 8 is a view similar to Figures 2 and 3 but illustrating the yhammering of the stem f a Valve body having a nubbin end whereby the stem is cold worked from the valve neck to'the nubbin only.

Figure 9 is a'viewgsimilar to Figure 8 but illus- Figure 10 is a longitudinal cross-sectional *ViewY of a coolant filled and plugged valve made froma valve body that has been cold worked according to the process illustrated in Figures 8 and 9.

Figure 11 is a longitudinal cross-sectional view i of a coolant filled and sealedvalve. made lby inwardly collapsing. the nubbin-.of a valve body thaty has lbeen cold-.workedas inFigu/rel and illustrate -ing the nubbin in dotted lines. fl As shown on the drawingst:I f

.In Figures 1 to 3th@ Areference character ,l0m designates ygenerally .a hollow poppet valvev blank having a" head 10a, a stem. |0b, and anoutwardly daring neck Inc joiningzthe lstem, andhead The head Illa has af mushroom-shaped., cav ity -l ll therein and the stem 10b, av cylindrical l,1o le.l2v l therethrough communicating -with'the head cav-3 ityll. I

ing, forging or extruding, or in any other suitable manner.

The blank III is acted on by a'pair of hammer dies I3 and I4 which are mounted in power-operated hammer holders I5 and I6 respectively.

The dies I3 and I4 cooperate to'form a throat I1 for receiving the neck Illc of the blank. This throat I1 converges inwardly to a cylindrical inner surface I8 which envelopes the stem Illb of the blank and has a smaller diameter than the initial diameter of the stem when the dies are fully closed. 'I'he dies are then relieved as at I 9 so that metal can iiow from the cylindrical portion into the relieved portion and the die thus has an active cylindrical surface I8 for cold working the metal of the stem IDb.

The stem IIIb, as pointed out above, has an interna] cylindrical hole or bore I2 therethrough. In accordance with this invention a mandrel 20 is inserted in the bore I2. This mandrel 20 has longitudinally extending circumferentially spaced flutes 20a alternating with longitudinally extending ribs 20h. The outer diameter of the mandrel is such that it snugly engages the internal wall of the valve blank. The mandrel 20 can have an4 enlarged knurled knob 2I at the end thereof to facilitate insertion and removal of the mandrel into and out of the valve stem.

The valve blank I0, with the mandr l inserted therein as shown in Figure 2, is placed between the dies I3 and I4 with the neck I0c thereof resting on the die seat I1. The dies are then reciprocated to hammer the valve stem IUb. The valve can be rotated in the dies during the hammering process or, alternatively of course, the dies could be rotated around the valve.

The cylindrical working surface of the dies thins down the valve stem IDD as illustrated at 22 and presses the stern around the mandrel so that the interior wall thereof will enter the fiutes 20a of the mandrel thereby forming longitudinal ribs on the interior wall of the stem. y

The entire length of the stem I0b is hammered by movement of the valve during the hammering i operation away from the seat I1 as illustrated in Figure 3. Alternately, of course, the dies could be moved downwardly along the valve stem.

The hammering operation is effected at temperatures below the recrystallization range of the valve metal. Preferably the hammering is effected when the valve blank is at room temperatures and after the blank has been suiciently formed so that it need not again be reheated to forging temperatures.v As a result the valve stem IIb is thinned down and cold worked.

Upon completion of the hammering along the entire length of the valve stem Illb the mandrel 2l is removed from the stem and a. valve blank 25 shown in Figure 4 is produced. 'I'he valve blank 25 has a cold worked stem 26- with a relatively thin wall. The interior of the stem 26 has longitudinally extending ribs 26a best shown in Figure 5. These ribs 28a alternate with grooves or serrations 2Gb.

'I'he longitudinally extending ribs 26a materially strengthen the stem wall and, at the same time, act as cooling fins for dispersing heat from coolant which is sealed in the hollow valve upon completing the production of a valve from the blank 25. Cooling material such as sodium is inserted into the hollow valve and the end of the valve stem is sealed by welding on a plug or a cap (not shown).

If desired the valve body I0 can have the stem nb thereof formed with an emarged nubbin end 12a in the valve.

IUd as shown in Figures 8 and 9 which is capable of being inwardly deformed to cooperate with a closure pin for plugging the valve as shown in Figure 10, or is capable of being inwardly collapsed to seal the valve as shown in Figure 11.

As shown inFigure 8 the valve stem I0b is cold hammered around a ribbed mandrel 20 by the dies I3 and I4 to thin down the stem as at 22 in the same manner described in connection with Figures 2 and 3. However the hammering is not permitted to progress to the end of the valve stem but is stopped at the nubbin as shown in the dotted line position of the dies. The stem Illb is thus cold worked from the neck Ic to the nubbin Ind.

As also shown in Figure 8, the mandrel 20 can have a tapered ribbed end 20c fitting into the throat portion of the valve body between the head cavity II and the stem hole I2. This permits the formation of a tapered ribbed throat The throat defining wall, due to the tapered throat, is somewhat thicker than the walls of the valve stem proper.

After cold working the stem down to the nubbin Id as shown in Figure 8, the nubbin is next cold worked around a tapered pin 21 by a pair of hammer dies 28 and 29 carried in power holders 30 and 3| as illustrated in Figure 9. The pin 21 is preferably not ribbed but has a smooth continuous tapered surface of circular cross section for shaping a smooth tapered hole 32 through the nubbin with the small end of the hole entering the larger and ribbed stem hole I2. The hammer dies 28 and 29 work down the nubbin 33 to a smaller diameter and collapse the nubbin inwardly around the pin. The hammering is effected along the entire length of the nubbin and the finished cold worked nubbin thus has a tapered hole 32 therethrough of lesser diameter than the hole I2 of the valve stem. The outside diameter of the cold worked and partially collapsed nubbin may be larger than the outside diameter of the stem but it is reduced to stem size by grinding. A valve spring retainer groove 34 (Figure 10) can also be ground or cut into the coldl worked and ground nubbin end of the stem.

A finished valve 25a is made from the cold worked tapered hole nubbin type of valve body by grinding and polishing the body to size, by inserting a coolant C such as sodium, into the head and stem cavities, and by driving a tapered sealing pin 35 into the hole 32. The pin 35 can have a head 35a forming the bottom of the valve stem. i

Instead of cold working the nubbin Ind around a tapered pin 21, a valve 25h as shown in Figure 11 can be made from a nubbin type of valve body by hammering the nubbin Illd completely shut after the coolant C has been inserted into the body provided that the valve metal is sumciently workable to permit complete collapsing of the nubbin. This will form a solid sealed end 36 on the valve stem.

The grooves 2Gb between the ribs 26a of the valves 25, 25a and 25h serve to break up any circumferentially extending defects in the interior of the stem. For example, even though the bore I2 of the blank I0 is carefully polished, some circumferentially extending scratches may remain in the interior stem wall. These scratches are highly dangerous because they form loci for fatigue cracks when the valve is subjected to heavy tension loads as in operation. By pressing' the stem around the fluted mandrel these scratches are either completely worked out of the metal or at least are broken up into short lengths because they never extend as deep as the grooves 26h and these grooves will thus divide the scratches. Any remaining short scratches are relatively unobjectionable.

The longitudinally extending flutes and ribs of the mandrel can have many forms and configurations. For example, as shown in Figure 6, the mandrel could be so shaped as to form more pronounced ribs 26e in the interior wall of the stem separated by rounded flutes 26d.

In still another embodiment of the invention the mandrel 20 can havea smooth, continuous polished cylindrical surface which will form a smooth, continuous, cylindrical surface 26e in the interior of the stem as shown in Figure 7.

In all embodiments of the invention the valve stem is cold-worked around a mandrel to improve the metallurgical characteristics of the stem metal. lin the preferred embodiments of the invention the interior surface of the valve stem is internally ribbed during the cold-Working operation.

in all embodiments of the invention, however, the poppet valves have materially strengthened hollow stems.

It will, of course, be understood that various details of construction may be varied through a wide range without departing from the principles of this invention and it is, therefore, not the purpose to limit the patent granted hereon otherwise than necessitatedby the scope of the v appended claims. A

We claim as our invention:

1. The method of increasing the tensile strength of hollow stemmed metal poppet valves which comprises rigidly supporting the inner wall of a hollow valve stem along its length at circumferentially spaced and circularly arranged narrow line portions thereof extending in a converging direction from the stem into the throat of the valve body, repeatedly hammering narrow cylindrical adjacent band areas of the stem and throat dening portion in succession along the length of the stem and throat dening portion to reduce' the stem to a constant outside diameter and to provide a tapered throat merging into the stem cavity, maintaining the temperature of the valve stem below the recrystallization temperature of the stem metal i during said hammering operations to cold work the stem, cutting the inner stem wall sufficiently deep to segregate into small increments any circumferential scratches in the inner wall of the stem at said supported line portions of the stem wall during said hammering operations, and simultaneously inwardly deforming the inner wall of the stem between the supported line areas thereof to form ribs in the stem cavity.

2. The method of increasing the tensile strength of hollow stemmed metal poppet valves which comprises rigidly supporting the inner Wall of a hollow valve stem along its length at circumferentially spaced and circularly arranged narrow line portions thereof extending from the stem into the throat of the poppet valve, repeatedly hammering narrow cylindrical ladjacent band areas of the stem and throat dening portion of the poppet valve in succession along the length of the stem and throat defining portion to reduce the stem to a constant outside diameter, maintaining the temperature of the Valve stem below the recrystallization temperature range of the stern metal during said hammering operations to cold work the stem, cutting the inner stem wall suflciently deep to segregate into small increments any circumferential scratches in the inner wall of the stem at said supported line portions of the stem Wall during said hammering operations, and simultaneously inwardly deforming the inner Wall of the stem and throat between the supported line areas thereof to form ribs in the. stem and throat cavity.

JOHN M. KERWIN. SAMUEL H. NORTON. 

